There are main three types of marine pumps on ship, impeller pumps(kinetic pumps), positive displacement pumps and ejectors.
1. Impeller Pumps(Kinetic Pumps)
Impellers will rotate at a very high speed in the pump casing and thus transmit mechanical energy to liquids. According to configurations of impellers and flow channel, there are centrifugal pumps, axial and mixed flow pumps and regenerative pumps.
2. Positive Displacement Pumps
There are moving parts and working chambers in this kind of pump. The volume of working chambers will change periodically due to the movement of the moving parts when the pump is in normal working condition, then these pumps can draw and discharge liquids. According to the movement of moving parts, these pumps fall into two kinds, i.e. reciprocating pumps and rotary pumps. The rotary pumps can be further classified into gear pumps, screw pumps, and vane pumps by the moving parts.
3. Ejectors
An ejectors doesn’t have any moving parts or mechanical driver, but instead, receviers energy from a pressurized motive or operating fluid that creates a pumping action as it passes through the ejector. According to the kinds of the operating fluid, there are water-jet ejectors, steam-jet ejectors and air-jet ejectors.
The impeller pumps and ejectors are not positive displacement pump since they increase the velocity of the delivered liquid to increase the energy of the liquid.
